دانلود رایگان مقاله انگلیسی کاهش جذب کوارتز در شناور سازی ذغال سنگ مرغوب توسط پلی آلومینیوم کلرید - الزویر 2019

ABSTRACT

Flotation tests using artificial mixtures of clean coal and quartz were conducted with and without the presence of sodium hexametaphosphate (SHMP) to study the effect of polyaluminum chloride (PAC) on quartz entrainment in fine coal flotation. Comparisons of flotation results show that the degree of quartz entrainment was greatly reduced using a suitable amount (e.g., 20 mg/L) of PAC in the absence of SHMP, however, significant changes of PAC on quartz entrainment did not appear in the presence of SHMP. The possible mechanisms responsible for the reduced quartz entrainment using PAC in fine coal flotation were investigated by particle size distribution measurements, zeta potential measurements, and interaction force calculations. Analysis of particle size distribution results reveals that when SHMP was not added, quartz particles were selectively aggregated with the addition of 20 mg/L PAC and the aggregation of quartz or coal particles was negligible at a high PAC dosage (e.g., 50 mg/L). Meanwhile, the aggregation of quartz particles induced by PAC was eliminated with the presence of SHMP. The electrostatic double layer repulsive force between quartz particles was calculated using the Deyaguin-Landau-Verwey-Overbeek (DLVO) theory with incorporating the results of zeta potential measurements. At 20 mg/L of PAC, the negative surface charge of quartz particle was neutralized and the electrostatic double layer repulsive force between quartz particles reached the minimum. These findings might be reasons of the aggregation of quart particles and therefore reduce the quartz entrainment in fine coal flotation.

4. Conclusions

The mitigation of quartz entrainment in fine coal flotation was successfully achieved with the addition of PAC at a suitable concentration (e.g., 20 mg/L). Analysis of results of particle size distribution, zeta potential and interaction energy between particles concludes that the mitigation of quartz entrainment is attributed to the aggregation of quartz particles induced by PAC. Through the zeta potential measurements and the DLVO interaction energy calculation, it demonstrated that PAC of 20 mg/L neutralized the negative charge on quartz surface and impaired the strength of the electrostatic double layer repulsive force between quartz particles. The presence of SHMP prevented the adsorption of PAC on quartz surface, resulting in the ineffectiveness of PAC on the reduction of quartz entrainment in fine coal flotation.

This work provides a new direction on improving the quality of coal flotation concentrates by selectively aggregating the gangue minerals. However, nowadays, the chemistry of recycled water to the flotation system in coal preparation plants in China has become more and more complicated due to the poorer quality of the run-of-mine coal and the increasing use of various chemicals for thickening. The present work has shown that the presence of dispersant SHMP has detrimental influence on the aggregation of quartz particles induced by PAC. Therefore, in the future work, it will be of interest to investigate and analyze the water chemistry in some typical coal preparation plants in China and study the synthetical effects of PAC and other typical residual chemicals in the recycle water on the mitigation of gangue entrainment.